We studied the dynamic fracture mechanical behavior of rock under different impact rates. The fracture experiment was a three-point bending beam subjected to different impact loads monitored using the reflected caustics method. The mechanical parameters for fracture of the three-point bending beam specimen under impact load are analyzed. The mechanism of crack propagation is discussed. Experimental results show that the dynamic stress intensity factor increases before crack initiation. When the dynamic stress intensity factor reaches its maximum value the crack starts to develop. After crack initiation the dynamic stress intensity factor decreases rapidly and oscillates. As the impact rate increases the cracks initiate earlier, the maximum value of crack growth velocity becomes smaller and the values of dynamic stress intensity factor also vary less during crack propagation. The results provide a theoretical basis for the study of rock dynamic fracture.
YANG Ren-shuYUE Zhong-wenSUN Zhong-huiXIAO Tong-sheGUO Dong-ming
Numerical simulation studies on blasting in ore-pass with charge both 250 kg and 500 kg are carried out.Adopting fluid-solid coupling method,the whole process from detonating to shockwave transference in the ore-pass reappears.The air shockwave's attenuation,chocking-up surface pressure and ore-wall press are analyzed.The results show that the biggest pressure of ore-wall happened at 0.43 m height,and the peak pressure are 167.0 MPa(250 kg)and 341.1 MPa(500 kg)individually.The choking-up zone's stress state from center to edge represents transition from press to strain,and the strain/press stress peak values are 9.2/4.8 MPa(250 kg)and 17.2/12.5 MPa(500 kg).The shockwave's attenuation values got from both experiential formula and simulation are compared,the experiential formula values are 2.54-3.49 times of the simulation results.
